Chronic total occlusion (CTO) is the complete blockage of a vessel and usually has serious consequences if not treated in a timely fashion. The blockage could be due to atheromatous plaque or old thrombus. One of the common procedures for treating CTOs of the coronary arteries is percutaneous transluminal coronary angioplasty (PTCA). During a PTCA procedure, a small incision is, typically, made in the groin. A guiding catheter over a guide wire is introduced into the femoral artery and advanced to the occlusion. Frequently, with gentle maneuvering, the guidewire is able to cross the stenosis. Then, a balloon-tipped angioplasty catheter is advanced over the guide wire to the stenosis. The balloon is inflated, separating or fracturing the atheroma. Some of the common steps involved in the PTCA procedure are the simultaneous injection of a contrast agent in the contra-lateral vessel, getting backup force or stabilization for a guide wire (which could invoke additional personnel to handle the catheter), puncturing the plaque, drilling or rotating the guide wire to push it through the dense plaque, etc. Because of the stiff resistance sometimes offered by dense plaque, one could be forced to use stiff wires. Occasionally, the wires could puncture the vessel wall calling for remedial measures.
Percutaneous treatment of coronary chronic total occlusions remains one of the major challenges in interventional cardiology. Recent data have shown that successful percutaneous recanalization of chronic coronary occlusions results in improved survival, as well as enhanced left ventricular function, reduction in angina, and improved exercise tolerance (Melchior J P, Doriot P A, Chatelain P, et al. Improvement of left ventricular contraction and relaxation synchronism after recanalization of chronic total coronary occlusion by angioplasty. J Am Coll Cardiol. 1987; 9(4):763-768; Olivari Z, Rubartelli P, Piscione F, et al. Immediate results and one-year clinical outcome after percutaneous coronary interventions in chronic total occlusions: data from a multicenter, prospective, observational study (TOAST-GISE). J Am Coll Cardiol. 2003; 41(10):1672-1678; Suero J A, Marso S P, Jones P G, et al. Procedural outcomes and long-term survival among patients undergoing percutaneous coronary intervention of a chronic total occlusion in native coronary arteries: a 20-year experience. J Am Coll Cardiol. 2001; 38(2):409-414).
However, because of the perceived procedural complexity of angioplasty in CTOs, it still represents the most common reason for referral to bypass surgery, or for choosing medical treatment (Bourassa M G, Roubin G S, Detre K M, et al. Bypass Angioplasty Revascularization Investigation: patient screening, selection, and recruitment. Am J Cardiol. 1995; 75(9):3C-8C; King S B, 3rd, Lembo N J, Weintraub W S, et al. A randomized trial comparing coronary angioplasty with coronary bypass surgery. Emory Angioplasty versus Surgery Trial (EAST). N Engl J Med. 1994; 331(16):1044-1050.)
The most common percutaneous coronary intervention (PCI) failure mode for CTOs is inability to successfully pass a guidewire across the lesion into the true lumen of the distal vessel (Kinoshita I, Katoh 0, Nariyama J, et al. Coronary angioplasty of chronic total occlusions with bridging collateral vessels: immediate and follow-up outcome from a large single-center experience. J Am Coll Cardiol. 1995; 26(2):409-415). To date, there is no consensus on how best to treat CTO after attempts with conventional guidewires have failed. Different strategies and specific devices for CTOs have been developed including the subintimal tracking and reentry with side branch technique, parallel wire technique, IVUS guided technique, and retrograde approach (Colombo A, Mikhail G W, Michev I, et al. Treating chronic total occlusions using subintimal tracking and reentry: the STAR technique. Catheter Cardiovasc Interv. 2005; 64(4):407-411; discussion 412; Ito S, Suzuki T, Ito T, et al. Novel technique using intravascular ultrasound-guided guidewire cross in coronary intervention for uncrossable chronic total occlusions. Circ J. 2004; 68(11):1088-1092; Kimura B J, Tsimikas S, Bhargava V, et al. Subintimal wire position during angioplasty of a chronic total coronary occlusion: detection and subsequent procedural guidance by intravascular ultrasound. Cathet Cardiovasc Diagn. 1995; 35(3):262-265; Matsubara T, Murata A, Kanyama H, et al. IVUS-guided wiring technique: promising approach for the chronic total occlusion. Catheter Cardiovasc Interv. 2004; 61(3):381386). However, none of these alternate strategies have provided satisfactory results for the most challenging of the CTOs.
Hence, it could be beneficial to have alternate techniques and devices that would recanalize a CTO without the shortcomings of the current techniques. CTOs that are hard to recanalize, either because of the tortuous anatomy of the diseased vessel, or because the proximal end of the stenosis is too hard for the guide wire to penetrate, or other characteristics of the CTO that would make the standard procedure vulnerable to failure would benefit from newer approaches to recanalize CTOs.